The present invention relates to silanol terminated polydiorganosiloxane-polyimide copolymers, or silicon hydride terminated polydiorganosiloxane-polyimide copolymers and room temperature, or low temperature condensation vulcanizable compositions obtained therefrom and methods for making such materials. More particularly, the present invention relates to the hydrosilation of norbornene terminated polyimides and the subsequent reaction of the resulting silicon-hydrogen terminated polyimides with silanol terminated polydiorganosiloxane.
Prior to the present invention, room temperature vulcanizable silanol terminated polydiorganosiloxanes, for example, silanol terminated polydimethylsiloxanes were available in either one-package or two-package systems based on the nature of the moisture sensitive cross-linking agents utilized in the composition. A typical one-package system is based on the use of methyltriacetoxysilane and a silanol terminated polydimethylsiloxane as shown by Ceyzeriat, U.S. Pat. No. 3,133,891. A two-package system as shown by Nitzsche et al, U.S. Pat. No. 3,065,194 requires the blending of silanol terminated polydimethylsiloxane with a curing catalyst, such as ethyl orthosilicate in combination with dibutyltindilaurate. The two-package system requires mixing of the curing catalyst with the silanol terminated polydimethylsiloxane prior to use.
The above described one-package and two-package room temperature vulcanizable compositions generally require the use of reinforcing filler, for example, a silica filler in amounts of from 5-300 parts, per 100 parts of silicone polymer, if improved tensile strength to the resulting cured silicone is desired. Another procedure available to improve the toughness of the cured silicone polymers is the introduction of silarylenesiloxy units into the polymer chain to produce a copolymer consisting essentially of diorganosiloxy units chemically combined with silarylenesiloxy units. Although these procedures substantially enhance the modulus (psi) of the silicone polymer, these procedures are uneconomic or do not achieve the degree of physical properties desired in the end product.
The present invention is based on the discovery that room temperature or low temperature condensation vulcanizable polydiorganosiloxane-polyimide copolymers have been found to provide elastomers exhibiting tensile strength in the range of 100 psi to 10,000 psi when cured with conventional room temperature vulcanizable curing catalysts. These silanol terminated or silicon hydride terminated polydiorganosiloxane-polyimide copolymers comprise by weight from 1 to 99% of polyimide blocks of the formula, ##STR1## chemically combined with from 99% to 1% of polydiorganosiloxane blocks of the formula, ##STR2## where R is a divalent radical selected from the class consisting of (a) aromatic hydrocarbon radicals having from 6-20 carbon atoms and halogenated aromatic hydrocarbon radicals having from 6-20 carbon atoms, (b) alkylene radicals having from 2-20 carbon atoms and cycloalkylene radicals having from 2-20 carbon atoms, (c) C.sub.(2-8) alkylene terminated polydiorganosiloxane, and (d) radicals included by the general formula, ##STR3## Q' is a member selected from the class consisting of ##STR4## x is a whole number from 1 to 5 inclusive, Q is a tetravalent radical selected from ##STR5## where D is a member selected from ##STR6## and R.sup.8 is a divalent radical selected from ##STR7## and divalent organic radicals of the general formula, ##STR8## X is a member selected from the class consisting of divalent radicals of the formula, ##STR9## y is an integer from 1 to 5, R.sup.1 -R.sup.6 are selected from hydrogen and C.sub.(1-8) alkyl radicals, R.sup.7 is the same or different C.sub.(1-13) monovalent hydrocarbon radical and substituted C.sub.(1-13) monovalent hydrocarbon radical, Y is a divalent radical selected from --O-- and --C(R.sup.1).sub.2 --, n is an integer equal to 0-200 inclusive, m is an integer equal to 1-2000 inclusive and p is equal to 0 or 1.
The silicon hydride terminated polydiorganosiloxane-polyimide copolymers of the present invention can be made by initially forming a norbornene terminated polyimide by effecting reaction between organic diamine, a norbornene anhydride and organic dianhydride, in accordance with the following equation: ##STR10## where Q, R, R.sup.1 -R.sup.6, n and Y are as previously defined.
The aliphatically unsaturated polyimide of formula (3) is thereafter hydrosilated with a silicon hydride having the formula, ##STR11## where r is 0 or 1, R.sup.9 is selected from hydrogen and R.sup.7, to produce silicon hydride terminated polyimide having the formula, ##STR12## where R-R.sup.7, Y, Q and n are as previously defined.
The silanol terminated polydiorganosiloxane polyimide copolymers of the present invention have the formula, ##STR13## where Z is a divalent group shown by formula (1), can be prepared by effecting reaction between the silicon hydride terminated polyimide of formula (5) and a silanol terminated polydiorganosiloxane of the formula, ##STR14## in the presence of an effective amount of condensation catalyst as defined hereinafter, where R.sup.7, R.sup.9 r and m are as previously defined and 1 is an integer having a value of from about 1 to 10.sup.4 inclusive.
Radicals included within R.sup.1 -R.sup.6 of formulas 1, 3 and 4 are, for example, hydrogen, methyl, ethyl, propyl, butyl, etc. Radicals included within R.sup.7 are, for example, aryl radicals and halogenated aryl radicals, for example, phenyl, chlorophenyl, tolyl, xylyl, biphenyl, naphthyl, etc.; alkenyl radicals, for example, vinyl, allyl, cyclohexenyl, etc.; C.sub.(1-8) alkyl radicals and halogenated alkyl, for example, methyl, ethyl, propyl, butyl, octyl, etc.